What do hair follicles house in the skin?

Correct Answer: C

Rationale: Hair follicles are structures in the skin that contain the hair shaft (the visible part of the hair) and the hair root (the part of the hair beneath the skin). The hair shaft is the portion of the hair that is visible above the skin, while the hair root is the part that extends below the surface into the follicle. Therefore, the correct answer is that hair follicles house the hair shafts and hair roots. Choices A, B, and D are incorrect because blood vessels are not housed within hair follicles, nerve endings are present but not housed within hair follicles, and sebaceous glands are often attached to hair follicles but not housed within them.

Correct Answer: C

Rationale: The correct answer is Calcium (Choice C). Calcium is essential for bone health and is stored in bones by the skeletal system. Bones act as a reservoir for calcium, playing a critical role in maintaining bone strength and density. Iron, sodium, and magnesium are important for various bodily functions but are not primarily stored in bones for bone health. Iron is crucial for oxygen transport, sodium helps regulate fluid balance, and magnesium is involved in over 300 enzymatic reactions in the body.

Correct Answer: B

Rationale: Calcium phosphate is the main component that gives bones their rigidity and hardness. It combines with calcium hydroxide to form hydroxyapatite crystals, which provide strength and structure to bones. Collagen, on the other hand, provides flexibility and tensile strength. Cartilage is a type of connective tissue found in joints, and ligaments are fibrous tissues that connect bones to other bones, but they do not contribute to the rigidity and hardness of bones.

Correct Answer: B

Rationale: Smooth muscle is the correct answer. It is found in the walls of blood vessels and helps regulate blood flow by contracting and relaxing to adjust the diameter of the vessels. Skeletal muscle, found attached to bones, is responsible for voluntary movements and is not typically found in blood vessel walls. Cardiac muscle is specific to the heart and responsible for pumping blood, not found in blood vessel walls. Striated muscle, another term for skeletal muscle, is characterized by its striped appearance under a microscope but is not present in blood vessel walls.

Correct Answer: C

Rationale: The nervous system is responsible for detecting touch (option A), regulating body temperature (option B), and controlling muscle movement (option D). Producing insulin (option C) is a function of the endocrine system, which produces hormones like insulin to regulate metabolism and glucose levels. Therefore, option C is the correct answer as it is not a function of the nervous system.